The advent of MPEG-2 digital video technology has brought the potential for vast improvements in the quality and quantity of programming. At the same time, this technology has significantly increased the complexity of managing video. An example of these complexities is the downstream insertion of a media signal having a first bitrate into a digital signal having a second bitrate. The first bitrate is not the same as the second bitrate, leading to either an over-utilization or an under utilization of bitrate. In a video advertisement (ad) context, local ad insertion systems enable cable multiplexers and broadcast affiliates to insert locally-generated commercials and short programs into remotely distributed regional programs before they are delivered to home viewers. This ad insertion can be accomplished by an architecture where ads are inserted by a downstream splicer on pre-encoded video streams. In this architecture, the original MPEG-2 or H.264 bitstream that is present in one or more of the channels in the multiplex is replaced by a bitstream of an ad that is read from an ad-server. Downstream ad-insertion affects the performance of closed-loop or open-loop encoding systems by modifying the multiplex that has been created by optimally distributing the available bits among different channels in which the inserted ad is not included. This results in reduced video quality or lesser number of channels in a given channel bandwidth since the downstream ad-insertion information is not incorporated while the multiplex is created. The bitrates of the inserted ads may not be exactly same as the bitrates of the MPEG-2 streams that are being replaced. Because of this, the aggregate bitrate of the multiplex after downstream ad-insertion can exceed the channel bandwidth which necessitates rate-reduction of one or more of the channels that results in degradation of the video quality. To avoid the need for the downstream rate-shaping in closed-loop, or open-loop, encoding, systems can generate a multiplex with an aggregate video bitrate that is lower than the transmission channel bandwidth in anticipation of ad-insertion downstream. This conservative approach supports ad-insertion but reduces multiplex capacity when there is no ad-insertion. Since ads are inserted typically for an average of 5-10 minutes over an hour, this approach results in underutilization of bandwidth for the rest of the time.
There is a need in the art for a system that supports downstream media signal insertion into a digital signal without affecting the quality of the digital signal.